Method of making piston rings



J. W. FORD.

METHOD OF MAKING PISTON RINGS.

APPLICATION FILED ]AN.8,1917.

Patented June 27, 1922.

UNITED STATES ATENT' OFFICE.

JOHN W. FORD, 013 ST. LOUIS, MISSOURI,-ASSIGNOR, BY MESNE ASSIGNMENTS, TO SPYROSEAL MANUFACTURING COMPANY, OF ST. LOUIS, MISSOURI, A CORPO- RATION OF MISSOURI.

Specification of Letters Patent.

Patented June 27, 1922.

Application filed January 8, 1917. Serial No. 141,111.

To all whom it may concern:

Be it known that I, JOHN W. F on, a citizen of the United States, and residing at St.

.Louis, Missouri, have invented the new and useful Improvement in Methods of Making structed of cast iron, as this metal gives the a greatest wearing qualities under the peculiar conditions of its operation. Such a ring must, however, be expansible, and in order to provide for expansion it is necessary to split the ring and overlap the ends in order to close the gap formed between the ends of the ring. Where, however, the ends overlap, and more particularly where they overlap for an extended part of the ring circumference, then it is diflicult to maintain the ends in overlapping engagement, for the reason that the tool employed to split the ring is necessarily of appreciable thickness. It is, of course, possible for short laps to form the ends by machining, but it is diflicult to obtain a good joint, even in such a lap, without considerable hand work. Where, of -course, the ends overlap for a considerable distance, then the only practical way of obtaining such overlapping is to split the ring for a part of its circumference. This means, however, that the ends are now sprung apart axially of the ring.

Now it is very important that the overlapping ends of a long lap ring he in substantially mutual engagement throughout their parting; if this is not the case, then carbon is liable to collect in the parting slot to such an extent, as to not only effect its engagement with the cylinder, but to even cause the ring to wedge in the piston; moreover the rapid movement of the piston in the cylinder is liable to cause vibration of the necessarily thin ends, so as to cause crystallization of the cast iron.

It would seem that the spaced overlapping ends could be brought into engagement by mere inversion, i. e., by springing one end over the other and then applying pressure.

This is, however, impractical for the following reason: In order to obtain elasticity and wearing qualities in a cast iron piston ring, it is necessary to select a hard close-grained iron. The elastic limit of such an iron is, however, very low, and the iron is, therefore. so brittle that mere inversion of the ends of the ring, or hammering after inversion, will not set the cast iron in inverted position, but the iron will break before any such set can be iven.

ne of the objects of this invention, therefore, is to provide a method whereby the overlapping ends of a long lap piston ring will be brought in substantially mutual. engagement throughout their parting.

Another object is to provide a process of closing the parting slot so as to secure uniform as well as permanent engagement of such overlapping ends.

Another object is to provide a novel method of making piston rings, whereby the ring is subjected to such treatment as to set the overlapping ends in such position as to be held together by the resiliency of the metal.

Further objects will appear from the dctail description taken in connection with the accompanying drawing, in which:

Figure 1 is a side view of the ring after itis out from the tub, and after the dividing slot has been cut therein;

Figure 2 is a similar view, showing the ends cut through to the slot;

Figure 3 is an end view of Figure 2;

Figure 4 is a view showing the ring with the overlapping ends inverted;

Figure 5 is a view showing the ring after treatment, with the ends reinverted;

Figure 6 is a side view'showing the finished ring; and,

Figure 7 is a perspective view of the finished ring.

Referring to the accompanying drawing, 1 designates a ring having overlapping ends 2 and 3, the ends being cut on a helix or spiralto form spirally or helically arranged overlapping end portions. The ring 1s so constructed that the ends overlap for an extended part of, and in the particular embodiment illustrated, for about one-half of the circumference of the ring. The overlapping ends lie'or are positioned, one within a recess in the other, so that the tips thereof can be and are blunt, as shown at 4, as this avoids breakage of the cast iron ends, and in order to bring about'this condition the ring body is cutto form shoulders 5. Gaps 6 "are formed between the ends 4 and the shoulders 5. so as to permit contraction of the ring when placed in the cylinder.

It will, therefore, be seen that in this ring the ends overlap for an extended part of the ring circumference, as distinguished from the ordinary short lap ring, in which the lap is merely suflicient to provide a seal;.in this particular embodiment the lap extends practi ally half way around the ring, the overlapping ends engaging along the line 8 which forms the parting.

The method cf making this ring will now be described. A casting in the form of a drum and known as a tub,?- is bored and turned down in the usual way, and the rings are cut off by suitable cutting tools. The ring is now placed in a milling machine and the cut a made helically and about half way around the ring, as shown in Figure 1. This is accomplished by an ordinary saw cutter, the ring being clamped between two plates in a rotatable head or work support. The gaps I) are now cut in a miller, so as to split the ring, as shown in Figures 2 and 3. This, of course, leaves a gap a extending circumfercntially of the ring, and which would render the ring leaky and unfit for use.

In accordance with this invention the ring is now inverted,v i. e., the end 2is sprung overon the other side of the end 3, thereby placing the ring under tension and the metal in the ring under strain, as shown in Figure 4.

The ring is now placed in an oven and heated to a cherry red (800 degrees ,the ring being kept at such a cherry red heat for a few minutes. This heat treatment sets the ring with the fibres in position. When the ring is inverted the molecules orfibres of the iron are placed under strains, and when the ring is heated to redness the strains are relieved and the molecules or fibres are rearranged so that the iron sets in that position. After the ring has been so heated, it is removed from the oven and allowed to coolin the air. The cool ring, therefore, has set so that any movement of the overlapping ends from the inverted position shown in Figure 4, back to their original positions, will place these ends under strain. In accordance with this invention, therefore, the ring is reinverted, as shown in Figure 5, i. e., the ends 2 and 3 are sprung back over one another, so as to place them in their original position. This, of course, places the ends under strain and results in the maintenance of the overlapping ends in close contact along the line 8 by the resiliency of the metal.

Due to the fact that the parting slot (1 has been taken up and closed, it is, of course, necessary to finish off the sides of the ring, and this is accomplishedin the usual way by placing the ring in a chuck and facing and grinding the end faces of the ring with the ring closed to normal diameter. The'rings are now placed inside of a drum, which is slightly oversize, clamped between two flanges, removed from the drum, and ground to diameter size on a cylindrical grinder.

The result is, therefore, a ring which possesses all of the desirable features of the ideal piston ring. The parting slot is substantially closed, even where the overlapping ends extend half way around the circumference of the ring. Moreover, these overlap ping ends are held in close contact due to the resiliency of the metal, brought about by this treatment. The operation of inversion and heating causes a uniform setting of the ring in such a position, and this, together with the dividing of the ring by a single cutter or saw, so as to form parallel-lined walls of the cut, causes substantially perfect contact of the overlapping ends throughout their length. I

In accordance with this invention, there is provided a practical long lap piston ring, that is one in which the ends thereof overlap for an extended part of the ring circumference, as distinguished from ordinary piston rings in which the ends overlap only sufficiently to form a gas seal between the free ends; in a long lap ring, however, the overlapping ends engage the cylinder walls for extended parts circumferentially, and, therefore, secure a more uniform engagement and a better gas tight joint between the cylinder and the piston. This is further enhanced by the ring structure, since a body of ring width is provided, so as to secure a sufficiently stifi juncture between the necessarily thin overlapping ends in order to obtain the required tension; and this is still further enhanced by providing a body of the ring width for an extended part of the ring circumference. The ring is of cast iron, as required in prac tice, and it is an integral and, therefore, a

' one-piece structure, so as to avoid the use of frail pieces of cast iron which are easily broken. The ends are moveover blunt-tipped and, therefore. breakage in this respect is avoided, as would be the case if the end tips came to feather edges.

In accordance with this invention, the extended overlapping ends are in mutual engagement throughout their parting; accordingly entrance of carbon and other matter between these ends is avoided, and moreover vibration of the necessarily thin overlapping ends is prevented. The treatment produces a ring in which these long overlapping ends are not only in substantially mutual engagement throughout their parting, but this engagement is a uniform one, as the straining and setting has been uniform from the center of each ring half to its tip, and not a strain or set for a short length of a thin end. Moreover the fact that the straining was that of a beam of thecircumferential length of the ring from one tip to the other, breakage and undue strain during straining is reduced to a minimum. Moreover, since the setting is of a uniformly strained structure, and in a manner to avoid rupture of th cast iron, the resultant set will be a permanent one. The resultant ring, therefore, hasthe characteristic of elasticity and permanency.

It is obvious that various changes may be made in the details within the scope of the appendant claims without departing from the spirit of this invention. It is, therefore, to be understood that this invention is not to be limited to thespecific details described and shown.

Having thus described the invention, what is claimed is:

l. The method of making piston rings, comprising, inverting the ring, heating the ring, and reinvertingthe ring.

2. The method of making split piston rings having overlapping ends, comprising,

inverting the ends of the ring, heating the ring, and reinverting the ends of the ring.

3. The method of making a split piston ring, having the ends thereof overlapping for about one-half of its circumference, comprising inverting the ends of the ring, subjecting the ring to treatment adapted to set the same in inverted position, and reinverting the ends of the ring.

4. The method of making a split piston ring, having the ends thereof overlapping for about one-half of its circumference, comprising inverting the ends of the ring, subjecting the ring to heat treatment at a temperature for a period suflicient to set the same in inverted position, and reinverting the ends of the ring.

5. The method of making piston rings, comprising, inverting the ring, subjecting the ring to heat treatment at a temperature and for a period sufficient to set the same in inverted position, and reinverting the ring.

6. The method of making piston'rings, comprising, inverting the ring, subjecting the ring to heat treatment at a temperature and for a period sufiicient to set the same in inverted position, reinverting the ring, and finishing the reinverted ring.

7. The process of forming a piston ring having overlapping end portions which comprises splittin a solid ring in a long zigzag cut extending 'circumferentially, inverting the split ring thereby formed, treating the inverted ring to remove molecular strains, and reversing the inverted ring.

8. The process of forming a piston ring having overlapping tapered ends which comprises splitting a solid ring in a long diagonal line, inverting the split ring thereby formed, treating the inverted ring to removemolecular strains, and reversing the inverted ring.

9. The process of forming a piston ring having overlapping spiral portions with tapered ends which comprises cutting a long spiral slot in the periphery of a solid ring,

the ends of said slot terminating near the 'helix having its contacting edges under tension to force them together sidewise.

11. The process of forming a spiral piston ring which comprises forming an open coil cylindrical helix and inverting it into a closed coil helix, treating the inverted ring to remove molecular strains, and reversing the inverted ring.

12. The process of forming a split piston ring which comprises cutting a spiral slot in an annular blank, severing the wall of the blank opposite each end of the slot, inverting the open coil helix thus formed, heating the inverted helix to a dull red and cooling slowly, and reinverting the helix.

13. The process of forming a one-piece piston ring which comprises splitting an annular blank lengthwise between its side faces around about one-half of its circumference, severing the edges of the blank on opposite sides, one at each end of the split portion, treating the blank to bring the lapping ends snugly together sidewise throughout their length, and finishing the si1 1ie faces of the blank to make them para el.

14.1 The process of forming a one-piece piston ring which comprises splitting an annular blank lengthwise between its side faces around about one-half of its circumference, cutting wide gaps through each of the edges of the blank on opposite sides, one at each end of the split portion, treating the blank to bring the lapping ends snugly together sidewise throughout their length, compressing the blank to close mid gaps and finishing the outer circumference of the blank to cylindrical form, and finishing the silrliel faces of the blank to make them para e 15.1n the art of making long lap cast iron piston rings, the process of closing the parting slot in the blank, comprising, strain-' 

